This invention relates to electrical wiring box structures and particularly to those of molded insulating material with special means for securing device mounting screws.
Electrical wiring boxes of insulating materials such as polyvinylchloride have been made and used with a variety of screw mounting means for securing devices within the box. In general, the approaches taken have suffered from either one of two drawbacks. One is that device installation time is undesirably long if the installer must drive a screw through an untapped bore hole. On the other hand, a tapped bore hole is undesirably expensive to make and may not provide the degree of mechanical security needed. This has led to the adoption of various kinds of metallic inserts within the bore hole that facilitate device mounting. One such example is that of Kinney U.S. Pat. No. 4,130,335, Dec. 19, 1978, which is herein incorporated by reference for its discussion of the general problem of achieving quick and easy mounting of devices within wiring boxes and previously proposed solutions thereto.
Among the objectives of this invention are economy, by avoiding a need of extra parts such as insertable metal clips. Another objective is security of holding devices by having the mounting arrangement include both very tight and secure gripping of the mounting screw. Use of some metal clips has the drawback of not giving a tight arrangement. The insertion of the screw may result in it being relatively secure against withdrawal but still not susceptible to being firmly tightened because the screw will continue to turn past the gripping elements of the metal clip. A further objective is fast assembly. The arrangement should be such as to allow rapid assembly.